I hope they will reveal a new style at E3. It was actually a good idea to make some unique themes since now we have a lot of possibilities. No Paper Mario please, stick to the platformers for now...SMB2/USA, Land or Odyssey would be great.
The dream would be a unique Yoshi Kotabe style but it's very unlikely since there is no specific mechanics attached to that, I don't think Nintendo would create a brand new style with brand new mechanics just for Maker.
Super paper Mario exists.